What is the Enneking staging system for osteosarcoma?

Updated: Jul 01, 2020
  • Author: Charles T Mehlman, DO, MPH; Chief Editor: Omohodion (Odion) Binitie, MD  more...
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The Enneking staging system is typically outlined as follows:

  • Low-grade tumor, intracompartmental – IA
  • Low-grade tumor, extracompartmental – IB
  • High-grade tumor, intracompartmental – IIA
  • High-grade tumor, extracompartmental – IIB
  • Any tumor (low- or high-grade, intra- or extracompartmental) with evidence of metastasis – III

The definition of a compartment is a central and crucial concept in this staging system. In general, a compartment may be defined as any individual bone (ie, each bone is a compartment unto itself), intra-articular space (ie, a purely intra-articular lesion is intracompartmental), or clearly identified fascially enclosed space (eg, the anterior compartment of the lower leg). Many of these compartments are the same ones that a surgeon would release in the setting of compartment syndrome; these relate much more to soft-tissue tumors than to bone tumors.

The Enneking staging system considers some areas of the body to be extracompartmental by definition, including the antecubital fossa, the inguinal region, the popliteal space, and intrapelvic and paraspinal lesions. Because of the unique challenges of spinal tumors, Weinstein, Boriani, and Biagin proposed an entirely separate staging system for these areas, commonly referred to as the WBB staging system.

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